1. Technical Field
The embodiments herein generally relate to chemical detection technology, and more particularly to chemical imaging of suspect chemically contaminated surfaces and standoff detection of subject chemical contaminants.
2. Description of the Related Art
A variety of systems and methods have been developed and used to detect and identify hazardous chemical and biological threat agents in the field. Chemical test kits that employ chemically reactive vapor-samplers and detection papers have long been used to detect chemical nerve agents, blood agents, and blister agents. While chemical kits are generally useful, they are designed to detect a limited range of conventional chemical agents that are toxic in the range of 10−3 g/person, provide no standoff protection, and may be prone to false negative and positive detections.
Systems that employ Ion Mobility Spectrometry (IMS) in which molecules are ionized and separated according to their differences in velocities through a gas in the presence of an electric field can, in theory, identify and detect a wide variety of chemical and biological warfare (CBW) agents. IMS systems, however, require direct exposure to the chemical agent and the instruments typically have insufficient resolving power to identify CBW agents before they have reached casualty producing levels.
Other systems employ passive infrared (PIR) imaging to detect airborne chemical threats such as nerve (GA, GB, and GD) and blister (H and L) agents based on the infrared spectrum of the agent. Currently fielded devices have been reported to detect aerosols at a distance of up to 5 km. Practical PIR detection systems have difficulty detecting low levels of CBW surface target contaminants because the surfaces are typically at thermal equilibrium and provide insufficient contrast to identify target contaminants. Additionally, background radiation and interference encountered in the field can also make detection difficult.
U.S. Pat. Nos. 5,241,179; 5,708,503; 6,464,392; 6,731,804; 7,038,789, and 7,262,414, the complete disclosures of which, in their entireties, are herein incorporated by reference, provide technologies for chemical threat detection. However, as threats continue to become more sophisticated, enhanced techniques are needed to provide suitable detection capabilities.
The U.S. military seeks, develops, and tests promising technologies capable of solving complex tactical standoff detection problems at a safe range. Scenarios of interest include chemical warfare agents (CWAs) in vapor/aerosol forms released into the open atmosphere vis-à-vis ordinance discharge, and surface contamination resulting from deposition and settling of the aerosol mass onto/into porous soil, sand, roads, bridges, etc. Accordingly, it would be advantageous to develop a sensor applied specifically to these problems.